Screen printing apparatus



Oct. 8, 1968 K. WATKIN I 3,404,623

SCREENPRINTING APPARATUS I 7 v I I Filed April 11, 1967 2 Sheets-Sheet 1Hlll lr wenlor z m,%ffm V I tlorneys Filed April 11, 1967 K. WATKIN3,404,623

SCREEN PRINT ING APPARATUS Oct. 8, 1968 2 Sheets-Sheet /4 E in; P W E K2 q ZLK /7 :25

/0 v g 1.1 E E A /4 93 A /4 lnvenlor Home United States Patent 3,404,623SCREEN PRINTING APPARATUS Kenneth Watkin, Chadderton, Oldham, England,assignor to Ferranti, Limited, Hollinwood, England, a company of GreatBritain and Northern Ireland Filed Apr. 11, 1967, Ser. No. 630,015Claims priority, application Great Britain, Apr. 12, 1966, 15,837/ 66 9Claims. (Cl. 101-35) ABSTRACT OF THE DISCLOSURE Screen printingapparatus which may be used for printing on either external or internalcylindrical surfaces. The screen is stretched between supports whichhave the same shape as the surface, and a similarlyshaped squeegee ismovable over the surface of the screen This invention relates to screenprinting apparatus.

Screen printing is used for printing on flat or cylindrical surfaceswhere the thickness of deposited ink is required to be greater thanprovided by other processes such as offset printing. The apparatus, inits simplest form, consists of a fine woven screen, usually of silk, anda squeegee for applying printing ink to the screen. The screen isrendered impervious to the printing ink by coating it with a suitablesealing material, and the matter to be printed is applied to the screenby removing this material from the appropriate parts of the screen. Inuse the screen is placed in close proximity to to the surface to beprinted, and the printing ink is applied to the screen by the squeegee.The ink passes through the screen, where the sealing material has beenremoved, on to the surface beneath.

Although this method is best suited to printing on flat surfaces, it isused for printing on the outside of objects in the form of circularcylinders, such as bottles and the like. The procedure is modifiedslightly in that the object is arranged to rotate as the screen movesover it, and the squeegee remains stationary.

It is not easy to modify the process for printing on surfaces which arenot flat or of circular cross-section, and methods other than screenprinting are commonly used. Similarly, printing on internal surfaces,such as the bore of a tube, is not possible by known screen printingmethods. Printing on the internal surfaces of the bodies may be done fordecorative effect where the body is translucent. In the case of opaquebodies it is sometimes necessary to form patterns of etch-resistant,conductive fluids on the internal surfaces. For example, in the formercase it may be desirable to print a pattern on an article such as a lampshade. An example of the latter case is the printing of an electricallyconductive pattern on the inner surface of a ceramic tube for a particleaccelerator vacuum chamber.

The object of the invention is to provide apparatus suitable forprinting on external or internal cylindrical surfaces as hereinafterdefined.

As used in this specification and claims the expression cylindricalsurface means a surface traced out by a straight line which movedparallel to itself and describes with each of its ends a fixed smoothclosed curve. This excludes cases where the fixed closed curves havesharp angles or corners in them, but includes both external and internalsurfaces.

According to the present invention apparatus for printing a requiredpattern on a cylindrical surface of a body comprises a screen ofsubstantially the same shape and dimensions as the cylindrical surfaceand which is impervious to a desired printing fluid except over an areaor areas defining the pattern, means for supporting the screen in closeproximity to that part of the surface on which the pattern is to beprinted, and a squeegee moveable in an axial direction over the screenon the side thereof remote from the surface and of such shape anddimensions that when the squeegee is: moved in said axial direction thescreen is pressed into contact with the surface.

The invention will now be described with reference to the accompanyingdrawings, in which:

FIGURES 1 and 2 show respectively plan and sectional side elevation viewof apparatus for printing a pattern on the internal surface of anannular body; and

FIGURE 3 shows a sectional side elevation of apparatus for printing apattern on the external surface of the same annular body.

In FIGURES 1 and 2, body 10 is of circular crosssection. A screen 11 ofsilk or some other suitable material is clamped to the rims of twowheel-shaped supports 12 and 13. Each support consists of a circular rim7, a central boss 8 and three radial spokes 9, as shown. The twosupports 12 and 13 are joined by three screws 14 passing through thespokes of the two frames. The two ends of the screws, and the part ofthe spokes through which they pass, are threaded in such a manner thatthe supports 12 and 13 may be moved apart by turning the screws 14 inone direction, and may be moved closer together by turning the screws inthe opposite direction. Thus the tension of the screen 11 may beadjusted. The two supports 12 and 13 and the screen are of substantiallythe same cross-sectional dimensions as the body and are of such a shapethat the screen may be supported very close to but not touching theinternal surface of the body 10 on which the required pattern is to beprinted.

A guide rod 15, capable of axial movement, passes through the centralboss 8 of each of the supports 12 and 13, and carries a main squeegee inthe form of a circular washer 16 clamped between two discs 17 by twonuts 18. The washer 16 is of flexible material and its dimensions aresuch that it presses the screen 11 outwards and into contact with thesurface of the body as shown.

A secondary squeegee 19 is supported close to the main squeegee and isdeflected upwards and away from the screen 11 by a deflector 20. Thedeflector is held in position by a spring 21 located between the upperdisc 17 and the deflector. The deflector may be moved downwards againstthe action of the spring by a tube 22 coaxial with the guide rod 15. Apeg 23 is fastened into the guide rod 15 and projects through a slot 24in the tube 22, and the slot is shaped so that rotation of the tuberelative to the guide rod causes the tube to move axially relative tothe guide rod. As the deflector 20 is moved downwards, the secondarysqueegee 19 moves towards the screen 11 and the main squeegee washer 16is moved away from the screen. The secondary squeegee 19 is of slightlysmaller diameter than the main squeegee washer 16, and does not pressthe screen 11 against the surface. The apparatus includes a jig (notshown) for locating the body 10 in the position shown.

The operation of the apparatus is described below.

A printing fluid is poured into the space between the screen 11 and themain squeegee washer 16, as shown at 25, and the squeegee is moved intoits lowest position. The apparatus is then placed inside the bore in thebody so that the screen 11 is close to the surface of the bore. Thedeflector is moved into the upper position such that the main squeegeewasher 16 presses the screen 11 against the surface of the bore. Thesqueegee is then moved axially upwards by means of the guide rod 15, andprinting fluid passes through the pattern on the screen and on to thesurface of the bore. At the end of the travel, the deflector 20 is moveddownwards to disengage the main squeegee. The squeegee is then moveddownwards, and the secondary squeegee skims the surface of the screenand carries the remaining printing fluid back to the initial startingposition.

FIGURE 3 shows a sectional side elevation of apparatus for printing onthe external surface of the same body. The apparatus is basically thesame, and the same references have been used on the drawings. Thedifference between the two embodiments is that in that of FIGURE 3, thescreen 11, supports 12 and 13, and the squeegees are arranged outsidethe body as shown. The guide rod and coaxial tube 22 shown in FIGURES 1and 2 are replaced by other means located outside the body. As before, ajig locates the body inside the apparatus in the position shown. Theoperation of the apparatus of this embodiment is very similar to thatalready described above. As before, the screen is of substantially thesame cross-sectional dimensions as the body.

It will be necessary to use different apparatus for each variation inthe size or shape of the bore. As stated in the introduction, theapparatus may be used for a wide variety of shapes, and the supports 12and 13, screen 11 and squeegees must be of substantially the same shape.

Many variations common to know screen printing methods may be applied tothe apparatus described above. For example, the thickness of thedeposited layer of printing fluid depends, amongst other factors, on thediameter of the threads making up the screen. Hence the layer thicknessmay be changed by using a screen made of fibres made of a differentthickness.

Similarly, materials other than silk may be used for the screen.

What I claim is:

1. Apparatus for printing a required pattern on a cylindrical surface ofa body, comprising a cylindrical screen of substantially the same shapeand cross-sectional dimensions as the cylindrical surface and which isimpervious .to a desired printing fluid except over an area or areasdefining the pattern, means for supporting the screen in close proximityto that part of the surface on which the pattern is to be printed, and amain squeegee movable in an axial direction over the screen on the sidethereof remote from the surface and being of such shape and dimensionsthat when the main squeegee is moved in said axial direction the screenis pressed into contact with said surface.

2. Apparatus as claimed in claim 1 which includes deflector meansoperable to deflect .the main squeegee away from said surface.

3. Apparatus as claimed in claim 2 which includes a secondary squeegeethe position of which is controlled by the deflector means such that thesecondary squeege is in light contact with the screen when the mainsqueegee is deflected away from the screen by the deflector means.

4. Apparatus as set forth in claim 1 in which the support means arearranged to support the screen in close proximity to an internalsurface.

5. Apparatus as set forth in claim 4 including a secondary squeegeedisposed in close proximity to the screen and movable in an axialdirection along the screen on the side thereof remote from the surface,and reflecting means between said squeegees operable to deflect the mainsqueegee away from the screen while maintaining the secondary squeegeein light contact with the screen.

6. Apparatus for printing a required pattern on an internal cylindricalsurface of a body comprising a cylindrical screen, said screen having across-sectional diameter smaller than the cross-sectional diameter ofthe 4 body, said screen being impervious to a desired printing fluidexcept over an area or areas defining the pattern and being yieldable ina radial direction, means for supporting the screen Within said body,and in close proximity to the internal surface of the body, a mainsqueegee, a secondary squeegee, means for supporting said main squeegeeand said secondary squeegee for movement in an axial direction along theinternal surface of said screen, said main squeegee being of circularshape in cross-section and of such dimensions that when the mainsqueegee is moved axially in one direction the screen is caused to yieldradially and be pressed into contact with the internal surface of thebody at the area adjacent the periphery of the main squeegee, anddeflecting means disposed between said main squeegee and said secondarysqueegee, said deflecting means being operable for deflecting said mainsqueegee in a direction away from the screen to allow movement axiallyin the other direction.

7. Apparatus for printing a required pattern on an internal cylindricalsurface of a body as set forth in claim 6 wherein said secondarysqueegee is of circular shape and has a diameter smaller than that ofsaid main squeegee, said secondary squeegee being operably connected tosaid deflecting means so as to be positioned in light contact with theinternal surface of the screen when moved in said other axial direction.

8. Apparatus for printing a required pattern on an external cylindricalsurface of a body comprising a cylindrical screen, said screen having across-section diameter greater than the cross-sectional diameter of thebody on which the pattern is to be printed and being yieldable in aradial direction, said screen being impervious to a desired printingfluid except over an area or areas defining the pattern, means forsupporting the screen in close proximity to the external surface of thebody and in surrounding relationship therewith, a main squeegee, asecondary squeegee, means for supporting said squeegees for movement inan axial direction along the outer surface of said screen, said mainsqueegee being of circular shape in cross-section and including a borehaving an internal diameter of such dimension that when the mainsqueegee is moved axially in one direction the screen is caused to yieldradially inward and be pressed into contact with the external surface ofthe body, and deflecting means disposed between said main squeegee andsaid secondary squeegee being operable for deflecting said main squeegeein a direction away from said screen so as to allow movement of the mainsqueegee axially in the other direction.

9. Apparatus for printing a required pattern as set forth in claim 8wherein said secondary squeegee is of circular shape and includes aninternal bore having a diameter greater than that of said main squeegee,said secondary squeegee being operably connected to said deflectingmeans so as to be positioned in light contact with the external surfaceof the screen when moved in the other axial direction 'while said mainsqueegee is deflected away from the screen.

References Cited UNITED STATES PATENTS 2,014,372 9/1935 Brickell l01-1142,863,382 12/1958 Giani l0l--l23 3,263,603 7/1966 Fuchs 101-1233,269,305 7/1966 Rossi 10l--l23 XR 3,055,339 9/1962 Pistole et al.118-408 ROBERT E. PULFREY, Primary Examiner.

C. D. CROWDER, Assistant Examiner.

